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Background It is still unknown whether COVID-19 vaccines induce a prothrombotic state or increase the hypercoagulable condition in subjects with a predisposition to thrombosis. Objectives We evaluated the coagulation profile in a series of healthy subjects who received the first dose of the BNT162b2 or the ChAdOx1 vaccines and assessed whether hypercoagulability developed. Patients/methods Volunteers among the staff of the University of Padua or health care professionals in the Padua University Hospital who had received either the ChAdOx1 or BNT162b2 vaccine in the previous 10 ± 2 days were eligible. A cohort of unvaccinated volunteers among family members of the University staff acted as control group. Global coagulation monitoring was assessed by whole blood rotational thromboelastometry, whole blood impedance aggregometry and thrombin generation. Platelet count was also obtained. Results One hundred and ninety subjects were enrolled: 101 (53.2%) received the ChAdOx1 vaccine and 89 (46.8%) the BNT162b2 vaccine. Twenty-eight non-vaccinated subjects acted as controls. Thromboelastometry parameters were all comparable among groups. Thrombin receptor activating peptide (TRAP)-, ADP- and ASPI-induced platelet aggregation were similar among groups, as well as platelet count. Endogenous thrombin potential (ETP) was comparable among groups. The results were confirmed after controlling for age, gender and hormonal. Considering women taking combined oral contraceptives or thrombophilia carriers, no differences were detected in thromboelastometry or thrombin generation parameters between subjects who received ChAdOx1 vs. BNT162b2 vaccines. Conclusions No significant activation of fibrinogen-driven coagulation, plasma thrombin generation or clinically meaningful platelet aggregation after ChAdOx1 or BNT162b2 vaccination was observed.

In patients with cirrhosis, particularly those with hepatocellular carcinoma (HCC), hypercoagulability may be associated with purported increased risks of portal vein thrombosis and cirrhosis progression. In this study, we extensively investigated hemostatic alterations potentially responsible for the thrombotic tendency in HCC, and evaluated whether such alterations were predictive of hepatic decompensation. Patients with cirrhosis at all stages were prospectively recruited and underwent an extensive hemostatic assessment, including all procoagulant factors and inhibitors, thrombin generation with and without thrombomodulin (TG), profibrinolytic and antifibrinolytic factors, and plasmin-antiplasmin complex. In study part 1 (case control), we compared alterations of coagulation and fibrinolysis in patients with cirrhosis with versus without HCC. In study part 2 (prospective), the subgroup of patients with decompensated cirrhosis was followed for development of further decompensation, and predictors of outcome were assessed by multivariate analysis. One-hundred patients were recruited (50 each with and without HCC). Severity of cirrhosis was comparable between groups. Median HCC volume was 9 cm3 (range: 5-16). Compared with controls, patients with HCC demonstrated a significantly more prothrombotic hemostatic profile due to increased TG and reduced activation of fibrinolysis, independent of cirrhosis stage. During a median follow-up of 175 days, 20 patients with decompensated cirrhosis developed further episodes of decompensation that were predicted by low FVII and high plasminogen activator inhibitor-1 levels, independent of Model for End-Stage Liver Disease score. Conclusion: Patients with cirrhosis with HCC have profound hyper-coagulable changes that can account for their increased thrombotic tendency. In contrast, hypercoagulability in patients with decompensated cirrhosis is more likely a consequence of chronic liver disease rather than a driver for cirrhosis progression.

Background Microvesicles (MVs) play a role in inflammation, coagulation, and vascular homeostasis in liver disease. Aim To characterize circulating plasma MVs profile in patients with decompensated cirrhosis and acute kidney injury (AKI). Methods We measured the levels of total, endothelial, platelet, tissue factor (TF)+, leukocyte and hepatocyte MVs by new generation flow-cytometry in a prospective cohort of patients with decompensated cirrhosis with and without AKI. Results Eighty patients with decompensated cirrhosis were recruited (40 each with and without AKI). Patients with cirrhosis with AKI had significantly higher calcein+ (total), endothelial, and platelet-MVs. Conversely, TF+, leukocyte, and hepatocyte-MVs were comparable between groups. Resolution of AKI was associated with significantly decreased total and endothelial-MVs that became comparable with those in patients without AKI. Platelet MVs significantly decreased but remained higher compared to patients without AKI. TF+MVs significantly decreased and became lower than patients without AKI. Leukocyte and hepatocyte-MVs remained unchanged. Creatinine (OR 4.3 [95%CI 1.8–10.7]), MELD (OR 1.13 [95%CI 1.02–1.27]), any bleeding (OR 9.07 [95%CI 2.02–40.6]), and hepatocyte-MVs (OR 1.04 [95%CI 1.02–1.07]) were independently associated with 30-day mortality. Conclusion AKI worsened vascular and cellular homeostasis in patients with cirrhosis, particularly by inducing endothelial dysfunction and platelet activation. AKI did not worsen systemic inflammation and hepatocytes activation.

High coagulation factor VIII (FVIII) levels comprise a common risk factor for venous thromboembolism (VTE), but the underlying genetic determinants are largely unknown. We investigated the molecular bases of high FVIII levels in 2 Italian families with severe thrombophilia. The proband of the first family had a history of recurrent VTE before age 50 years, with extremely and persistently elevated FVIII antigen and activity levels (>400%) as the only thrombophilic defects. Genetic analysis revealed a 23.4-kb tandem duplication of the proximal portion of the F8 gene (promoter, exon 1, and a large part of intron 1), which cosegregated with high FVIII levels in the family and was absent in 103 normal controls. Targeted screening of 50 unrelated VTE patients with FVIII levels ≥250% identified a second thrombophilic family with the same F8 rearrangement on the same genetic background, suggesting a founder effect. Carriers of the duplication from both families showed a twofold or greater upregulation of F8 messenger RNA, consistent with the presence of open chromatin signatures and enhancer elements within the duplicated region. Testing of these sequences in a luciferase reporter assay pinpointed a 927-bp region of F8 intron 1 associated with >45-fold increased reporter activity in endothelial cells, potentially mediating the F8 transcriptional enhancement observed in carriers of the duplication. In summary, we report the first thrombophilic defect in the F8 gene (designated FVIII Padua) associated with markedly elevated FVIII levels and severe thrombophilia in 2 Italian families.

A large number of daily requests to exclude possible prothrombotic risk factors for coronavirus disease 2019 (COVID-19) vaccines were received. Our aim was to longitudinally evaluate coagulation profiles in a series of healthy subjects who received COVID-19 vaccination and assess hypercoagulability thereafter. Volunteers awaiting a first or second dose of either the ChAdOx1 or BNT162b2 vaccine were enrolled. Venous samples were obtained at baseline (before the vaccine) and longitudinally 3 ± 2 days (T1) and 10 ± 2 days after the vaccine (T2). Global coagulation monitoring was assessed via platelet count, whole blood thromboelastometry and impedance aggregometry, plasma thrombin generation, and anti-platelet factor 4 (PF4)/heparin immunoglobulin G antibodies. One hundred and twenty-two subjects were enrolled (61 [50%] ChAdOx1 and 61 BNT162b2). The ChAdOx1 cohort showed a slight but transient increase in thrombin generation (mainly endogenous thrombin potential [ETP] with thrombomodulin and ETP ratio) at T1, which promptly decreased at T2. In addition, the second dose of either vaccine was associated with increased thrombin peak, ETP with thrombomodulin, and ETP ratio. At baseline, 3.2% of the ChAdOx1 cohort and 1.6% BNT162b2 cohort were positive for PF4/heparin antibodies with a stable titer through T1 and T2. No relevant differences were detected in platelet count and aggregation, or thromboelastometry parameters. No thrombotic or hemorrhagic events occurred. We can confirm that no clinically meaningful hypercoagulability occurred after either vaccine, albeit keeping in mind that thrombin generation may increase in the first days after the second dose of either vaccine and after the first dose of the ChAdOx1 vaccine.

Hypercoagulability and hypofibrinolysis in acutely decompensated cirrhosis (AD) may be implicated in disease progression and haemostatic complications. We conducted a prospective study to: (1) characterise haemostatic alterations in AD; (2) evaluate whether such alterations can predict acute-on-chronic liver failure (ACLF) and bleeding/thrombosis.Hospitalised individuals with AD were prospectively recruited and underwent an extensive haemostatic profiling including coagulation factors, thrombomodulin-modified thrombin generation assay with evaluation of endogenous thrombin potential (ETP; marker for plasmatic hypercoagulability), fibrinolytic factors, and plasmin-antiplasmin complex (fibrinolysis activation marker). Inflammation severity was assessed by C-reactive protein (CRP). In part 1 of the study, we compared haemostasis in AD vs. controls (stable decompensated and compensated cirrhosis). In part 2 of the study, we prospectively followed individuals with AD for 1 year and investigated predictors of ACLF and bleeding/thrombosis.A total of 169 individuals with AD were recruited (median model for end-stage liver disease score 20; CLIF-C AD 54). Compared with controls, AD was associated with more pronounced hypercoagulability (ETP: 871 vs. 750 vs. 605 nmol/L per min; p0.0001), without differences in fibrinolysis activation. During follow-up, 55 individuals developed ACLF. CLIF-C AD, CRP, and Child-Pugh were independently associated with ACLF. A predictive model combining these variables (Padua model) accurately identified individuals at higher risk of ACLF (AUROC 0.857; 95% CI 0.798-0.915; sensitivity 74.5%, specificity 83.3%). Notably, CRP and progression to ACLF, but not baseline coagulopathy, were associated with bleeding (n = 11); CRP and antifibrinolytic factor PAI-150 ng/ml were associated with thrombosis (n = 14). The prognostic value of the Padua model was validated in an independent, bicentric European cohort (N = 301).Inflammation severity, and not coagulopathy, is the most important predictor of ACLF and bleeding in AD. The Padua model can be used to identify individuals with AD at risk of ACLF.A better understanding of haemostasis in individuals with acutely decompensated cirrhosis may help to identify those at higher risk of progression and complications. In this prospective study, we found no significant association between alterations of haemostasis and cirrhosis progression, indicating that the assessment of haemostatic alterations is not useful to identify those at risk. However, we found that C-reactive protein (a simple blood test that reflects severity of inflammation) and severity of chronic liver disease itself (as assessed by specific scores) were associated with cirrhosis progression and development of bleeding complications. Therefore, we developed a simple predictive model - based on C-reactive protein and liver disease scores - that, if validated by independent studies, could be used in clinical practice to assist physicians in identifying individuals with decompensated cirrhosis at higher risk of disease progression and death (i.e. in whom to consider an expedited evaluation for liver transplantation).

Studies on platelet aggregation in cirrhosis are controversial because interpretation of platelet function is challenged by thrombocytopenia. We conducted a prospective study to investigate whole blood platelet aggregation in cirrhosis and its association with liver-related outcomes.Platelet aggregation was assessed by whole blood aggregometry (Multiplate®). To overcome the influence of platelet count and compare cirrhosis with thrombocytopenia vs. controls with normal platelet count, we calculated a ratio between platelet aggregation and platelet count (PLT ratio). Then, we prospectively followed patients with cirrhosis and ascertained predictors of decompensation, transplantation, and death.Two-hundred and three patients with cirrhosis were prospectively recruited (77% decompensated). PLT ratio was significantly higher in cirrhosis than in those with chronic hepatitis and healthy individuals (0.44 vs. 0.25 and 0.26, respectively; p0.0001). In cirrhosis, the ratio increased with disease severity (Child-Pugh class CBA) and was particularly elevated in decompensated patients with severe thrombocytopenia. Among decompensated patients, 65 had further decompensation, underwent transplantation, or died during a 6-month follow-up. On multivariate analysis, PLT ratio (odds ratio 1.87; 95% CI 1.23-2.84; p = 0.003) and MELD score (odds ratio 1.05; 95% CI 1.01-1.08; p = 0.01) were independently associated with outcome. The relative risk of events was 7.5-fold higher in patients with PLT ratio0.75 vs. patients with PLT ratio0.25 (95% CI 2.5-21.9; p = 0.003). The increased PLT ratio, its discriminative ability for composite outcome, and the prognostic value of PLT ratio0.75 were confirmed in an independent cohort of hospitalized patients with decompensated cirrhosis (n = 41).Patients with cirrhosis, particularly when decompensated, exhibit significantly increased whole blood platelet aggregation. Decompensated patients with a PLT ratio0.75 have a80% probability of further decompensation, transplantation, or liver-related death within 6 months.In patients with cirrhosis, previous studies have suggested that platelets (i.e. circulating blood cells that help form clots to stop bleeding) are dysfunctional. In particular, these studies suggested that platelet aggregation (the process by which platelets adhere to each other to form clots) is reduced. Since platelet aggregation is important for clot formation, it has been hypothesized that alterations of platelet aggregation may be responsible for the increased risk of bleeding observed in patients with cirrhosis. Our study demonstrates: i) that platelet aggregation in patients with cirrhosis is higher than in healthy individuals; ii) that platelet aggregation in patients with decompensated cirrhosis (i.e. those who have already experienced some complications of cirrhosis) is particularly elevated and associated with risk of further complications and death.

Background: Low plasma levels of protein C or protein S are associated with venous thromboembolism rather than myocardial infarction. The high coagulant activity in patients with thrombophilia with a (familial) defect in protein C or S is explained by defective protein C activation, involving thrombomodulin and protein S. This causes increased plasmatic thrombin generation.Objective: Assess the role of platelets in the thrombus- and fibrin-forming potential in patients with familial protein C or protein S deficiency under high-shear flow conditions.Patients/Methods: Whole blood from 23 patients and 15 control subjects was perfused over six glycoprotein VI-dependent microspot surfaces. By real-time multicolor microscopic imaging, kinetics of platelet thrombus and fibrin formation were characterized in 49 parameters.Results and Conclusion: Whole-blood flow perfusion over collagen, collagen-like peptide, and fibrin surfaces with low or high GPVI dependency indicated an unexpected impairment of platelet activation, thrombus phenotype, and fibrin formation but unchanged platelet adhesion, observed in patients with protein C deficiency and to a lesser extent protein S deficiency, when compared to controls. The defect extended from diminished phosphatidylserine exposure and thrombus contraction to delayed and suppressed fibrin formation. The mechanism was thrombomodulin independent, and may involve negative platelet priming by plasma components.

Hyper-functional platelets are being proposed as a potential therapeutic target in multiple cancers. Whether this can be considered in patients with cirrhosis and hepatocellular carcinoma (HCC) is unknown as their platelet function has not yet been investigated. We evaluated platelet function in cirrhosis patients with HCC. Patients with cirrhosis with and without HCC were prospectively recruited. Platelet aggregation, a marker of platelet function, was assessed by impedance aggregometry with adenosine diphosphate (ADP), arachidonic acid (ASPI), and thrombin (TRAP) stimulation. Plasmatic levels of Von Willebrand factor antigen (VWF) were also determined. One-hundred patients were recruited (50 cirrhotics with and 50 without HCC). Cirrhosis severity by Child class and platelet count were comparable between cirrhotics with and without HCC. Cirrhotics with HCC had higher ADP- (45 vs. 28, p &lt, 0.001), ASPI- (47 vs. 28, 0.001), and TRAP- (85 vs. 75, p = 0.01) induced platelet aggregation than cirrhotics without HCC, all indicative of platelet hyper-function. The relatively increased platelet aggregation in patients with HCC was confirmed after adjusting the analysis for platelet count/severity of thrombocytopenia. Levels of VWF were higher in patients with vs. without HCC (348 vs. 267, p = 0.006), particularly in compensated cirrhosis. In patients with cirrhosis, HCC is associated with increased platelet aggregation and higher VWF. The clinical implications of these findings deserve further investigation.

Background & Aims Understanding factors responsible for the increased bleeding tendency in acute‐on‐chronic liver failure (ACLF) would improve the management of these complications. We investigated coagulation alterations in ACLF and assessed whether they were predictive of bleeding. Methods Cirrhosis patients with ACLF (cases) and acute decompensation (AD, controls) were prospectively recruited and underwent an extensive haemostatic assessment including standard tests, pro and anticoagulant factors, thrombomodulin‐modified thrombin generation (TG) and thromboelastometry (ROTEM®). In study part 1 (case‐control), we compared coagulation in ACLF vs AD. In study part 2 (prospective), all patients were followed for bleeding, and predictors of outcome were assessed. Results Ninety‐one patients were included (51 with ACLF, 40 with AD). Infections and ascites/renal dysfunction were the most common precipitating and decompensating events. Platelet count was lower while INR and activated partial thrombin time were longer in ACLF cohort vs AD. Regarding clotting factors, fibrinogen and factor VIII were comparable between groups while protein C and antithrombin were significantly reduced in ACLF. Endogenous thrombin potential by TG was comparable between groups. Clotting formation time and clot stability by ROTEM® were significantly lower in ACLF, indicative of a more hypocoagulable state. No haemostasis alteration could discriminate between patients who had bleeding complications during hospitalization and those who did not. Conclusion We found coagulation changes in ACLF to largely overlap with that of AD and evidence of preserved coagulation capacity in both groups. ROTEM alterations were indicative of a more pronounced hypocoagulable state in ACLF; however, no correlation was found between such alterations and bleeding.

Objectives Thrombin generation (TG) with and without thrombomodulin (TM) was evaluated in COVID-19 patients with different disease severity and thromboprophylaxis regimen, in order to understand the prothrombotic profile. Methods We enrolled consecutive patients with confirmed diagnosis of COVID-19 admitted to Medical Departments (MD) or Intensive Care Units (ICU), and 54 healthy controls. Results Eighty-nine patients were included (mean age 60.4±16.1 years, 68.5% male); 33.7% admitted to ICU. Twenty-four patients (26.9%) were enrolled before thromboprophylaxis administration; 45 patients (50.6%) received standard and 20 (22.5%) intermediate sub-therapeutic dose thromboprophylaxis. Overall, patients with COVID-19 showed a TG profile comparable to that of healthy subjects (i.e. comparable peak height, endogenous thrombin potential [ETP] with and without TM). The only exception was lag time and time to peak, prolonged in COVID-19 patients vs. controls. MD patients showed a similar TG profile to healthy controls, and ICU patients showed significantly decrease ETP (p=0.030) compared to MD. As for thromboprophylaxis, TG profile was significantly increased in COVID-19 patients without thromboprophylaxis vs. controls and vs. those with thromboprophylaxis. In this latter group, ETP inhibition was significantly decreased (p=0.0003) and positively correlated with anti-Xa activity (r=0.49, p=0.0017). However, patients with thromboprophylaxis had similar TG profile vs. controls. Intermediate dose thromboprophylaxis more effectively inhibited TG in severe COVID-19 patients by increasing ETP inhibition via ETP with TM reduction vs. standard dose. Conclusions COVID-19 patients showed increased TG at diagnosis. Standard thromboprophylaxis reduced TG to levels of healthy controls. Intermediate sub-therapeutic thromboprophylaxis more effectively inhibited TG by decreasing ETP with TM.

Background In this prospective cohort study, we aimed to evaluate the efficacy and safety of direct oral anticoagulants (DOACs) versus heparin/vitamin K antagonists for the treatment of venous thromboembolism (VTE) in patients with inherited thrombophilia. Methods and Results We enrolled consecutive patients with acute VTE and inherited thrombophilia treated with DOACs (cases) or heparin/vitamin K antagonists (controls), matched for age, sex, ethnicity, and thrombophilia type. End points were VTE recurrence and bleeding complications; residual vein thrombosis and post‐thrombotic syndrome; VTE recurrence after anticoagulant discontinuation. Two hundred fifty‐five cases (age 52.4±17.3 years, Female 44.3%, severe thrombophilia 33.1%) and 322 controls (age 49.7±18.1 years, Female 50.3%, severe thrombophilia 35.1%) were included. The cumulative incidence of VTE recurrence during anticoagulation was 1.09% in cases versus 1.83%, adjusted hazard ratio (HR) 0.67 (95% CI, 0.16–2.77). The cumulative incidence of bleeding was 10.2% in cases versus 4.97%, HR 2.24 (95% CI 1.10–4.58). No major bleedings occurred in cases (versus 3 in controls). No significant differences regarding residual vein thrombosis and post‐thrombotic syndrome. After anticoagulant discontinuation, DOACs yielded a significantly lower 2‐year VTE recurrence risk versus traditional anticoagulants (HR, 0.61 [95% CI, 0.47–0.82]). Conclusions DOACs and heparin/vitamin K antagonists showed a similar efficacy in treating VTE in patients with thrombophilia. Although major bleeding episodes were recorded solely with heparin/vitamin K antagonists, we noted an overall increased bleeding rate with DOACs. The use of DOACs was associated with a lower 2‐year risk of VTE recurrence after anticoagulant discontinuation.

Background & Aims The long-term impact of sustained virological response (SVR) after direct-acting antivirals (DAAs) on the hypercoagulability associated with HCV cirrhosis is unknown. We longitudinally evaluated the effect of DAAs treatment on cirrhotic coagulopathy. Methods Results Pro- and anticoagulant factor levels and thrombin generation were assessed in patients with HCV-related cirrhosis at baseline, end of therapy (EOT), at 12, 24 and 48 weeks (W) after EOT. Fifty-eight patients were enrolled (86% Child's A). SVR was 100%. Median factor VIII activity significantly decreased at EOT, 12 weeks and 24 weeks compared with baseline, whereas protein C significantly increased at 24 weeks and 48 weeks. Cirrhotic patients showed a slight but sustained increase in endogenous thrombin potential (ETP) with a statistically significant difference at EOT, 12 weeks, 24 weeks and 48 weeks compared with baseline. Conversely, thrombomodulin-modified ETP was elevated before treatment and decreased over time to normal levels at 24 weeks and 48 weeks. The ETP ratio decreased slowly at EOT and 12 weeks, and was significantly decreased at 24 weeks and 48 weeks compared with baseline (P

BACKGROUND AND AIMS Recent evidence suggests that acute kidney injury (AKI) is the main predictor of postparacentesis bleeding in patients with cirrhosis. To assess the factors responsible for bleeding tendency in AKI, we performed a prospective study comparing all three aspects of hemostasis (platelets, coagulation, and fibrinolysis) in patients with decompensated cirrhosis with and without AKI. APPROACH AND RESULTS Primary hemostasis assessment included platelet aggregation and secretion (platelet function markers) and von Willebrand factor. Secondary hemostasis assessment included pro-coagulant (factor VIII and factor XIII) and anti-coagulant (protein C, protein S, and antithrombin) factors and thrombin generation. Tertiary hemostasis assessment included fibrinolytic factors and plasmin-antiplasmin complex. Eighty patients with decompensated cirrhosis were recruited (40 each with and without AKI). Severity of cirrhosis and platelet count were comparable between groups. Median serum creatinine was 1.8 mg/dL and 0.8 mg/dL in patients with and without AKI, respectively. At baseline, patients with cirrhosis and AKI had lower platelet aggregation and secretion, indicative of impaired platelet function (increased bleeding tendency), without differences in von Willebrand factor. Regarding coagulation factors, factor VIII was higher, whereas protein C, protein S, and antithrombin were all lower, which, together with increased thrombin generation, indicate hypercoagulability. In contrast, factor XIII was lower in AKI (increased bleeding tendency). Finally, while both hypofibrinolytic and hyperfibrinolytic changes were present in AKI, a higher plasmin-antiplasmin complex indicated a hyperfibrinolytic state. After AKI resolution (n = 23 of 40), platelet function and coagulation improved to levels observed in patients with cirrhosis patients without AKI; however, fibrinolysis remained hyperactivated. CONCLUSIONS In patients with decompensated cirrhosis, AKI is associated with both hypocoagulable and hypercoagulable features that can potentially increase the risk of both bleeding and thrombosis.

BACKGROUND & AIMS The eradication of Hepatitis C (HCV) infection by direct-acting antiviral (DAAs) agents has been linked to an amelioration of liver synthesis and regression of fibrosis. Although changes in number and type of circulating microvesicles (MVs) have been reported in cirrhosis, conclusive data on the effect of DAAs treatment on MVs profile in HCV cirrhotic patients remain scarce. METHODS We measured the levels of endothelial, platelet and hepatocyte MVs, as well as MVs-expressing versican core protein (VCAN+) in patients with HCV-related cirrhosis at baseline, end of treatment (EOT), at 12, 24 and 48 weeks (W) after EOT by new generation flow cytometry. RESULTS Fifty-eight patients were enrolled (86% Child's A). MVs were increased at EOT vs baseline, though only platelet MVs revealed a statistically significant difference (P

Although human megakaryocytes can synthesize factor V (FV), platelet FV derives largely from endocytosis of plasma FV. Recently, it has been shown that plasma transfusions can replenish the platelet FV pool in parahaemophilic patients. Here we corroborate this finding by showing FV endocytosis by ex vivo differentiated megakaryocytes derived from patients with inherited parahaemophilia. Mononuclear stem cells isolated from peripheral blood of healthy subjects and of three patients with severe parahaemophilia were cultured in the presence of thrombopoietin and interleukin-3 and differentiated into CD41-positive polynucleated megakaryocytes. Exogenous purified FV was added to the culture medium to evaluate FV endocytosis. Immunofluorescence staining revealed abundant FV expression in megakaryocytes derived from healthy donors, but no FV expression in those derived from patients with severe parahaemophilia. However, after the addition of purified FV to the culture medium, megakaryocytes from parahaemophilia patients became positive upon FV immunostaining, suggesting endocytosis of exogenous FV. Endocytosed FV retained factor Xa-co-factor activity as assessed by a prothrombin time-based functional test in megakaryocyte lysates. Addition of exogenous FV to culture medium can restore the FV content of megakaryocytes derived from patients with severe FV defects. This rescue mechanism can have important clinical implications in the management of parahaemophilia patients.

Objective— Two different prothrombin variants, p.Arg596Leu and p.Arg596Gln, conferring antithrombin resistance to patients with venous thromboembolism have been recently reported. Here, we describe a novel substitution affecting Arg596 of prothrombin molecule (Arginine596 to Tryptophan or p.Arg596Trp or Arg221aTrp in the chymotrypsinogen numbering system or prothrombin Padua 2) in 2 Italian families with venous thromboembolism. Approach and Results— Prothrombin Padua 2 has been characterized either in plasma of carriers or using Arg596Trp recombinant prothrombin. Routine coagulation tests, thrombin generation, and antithrombin resistance tests were performed, as well as measurement of the levels of thrombin–antithrombin complexes. All carriers were heterozygotes and presented with a mild reduction of the prothrombin activity. Thrombin generation in carriers showed only a markedly prolonged decay. This finding was confirmed in plasma reconstituted with Arg596Trp recombinant prothrombin mimicking a homozygous condition, which showed longer decay and higher endogenous thrombin potential in thrombin generation than wild-type recombinant prothrombin reconstituted plasma. Patient’s plasma as well as Arg596Trp recombinant prothrombin showed a clear thrombin resistance to antithrombin inactivation. These findings were supported by the assessment of thrombin–antithrombin complexes formation, which was strongly reduced for Arg596Trp recombinant prothrombin as compared with wild-type recombinant prothrombin. In a series of 400 unrelated consecutive patients with venous thromboembolism, 2 carriers of prothrombin Padua 2 were found (estimated prevalence of 0.5%). Conclusions— Our study showed that prothrombin Padua 2 induces antithrombin resistance and is associated with an increased risk of venous thromboembolism. Codon 596 (CGG) of prothrombin is a hot spot for mutations, which constitute a new and relatively frequent cause of inherited thrombophilia.

A definitive relationship between adiposity and MP production is yet to be demonstrated. The aim of our study was to prospectively evaluate the levels of microparticles (MP) in a group of 20 III degree obese patients before and after weight loss. Plasma levels of annexin V-MP, endothelial-derived MP, platelet-derived MP (CD61+ and P-Selectin+), leukocyte-derived MP, tissue factor-bearing (TF+) and CD36+MP were prospectively measured in 20 patients with III degree obesity (BMI ≥ 40 kg/m(2)) before (T0) and 3 (T3) and 12 (T12) months after sleeve gastrectomy (SLG). Obese patients had lost 18 % of their body weight at T3 and 41 % at T12. We find that considering all MP, except for endothelial-derived MP, which had significantly decreased at T3, all MP subtypes had significantly decreased at T12. At T12, subjects showed a higher median level of all types of MP, except endothelial-derived MP, compared to T3, but without a statistically significant difference. The percentages of reduction of all the MP were significantly correlated with the percentage of reduction of BMI. The reductions of leukocyte-derived, TF+ and CD36+MP were significantly correlated with the reduction of leptin. Moreover, the reductions of leukocyte-derived and CD36+MP were significantly correlated with hs-CRP decrease. The decrease of BMI post-SLG in morbid obesity was matched with a decrease of circulating MP of endothelial, platelet, leukocyte origin, TF+ and CD36+. A trend of slight increase in all MP subtypes, except endothelial-derived, was detected 12 months after gastrectomy, indicating a possible underlying slow low-grade inflammatory/hypercoagulability state from adipose tissue before the potential overt weight gain.

Introduction Severe congenital factor V (FV) deficiency is a rare bleeding disorder characterized by very low/undetectable levels of FV. Fresh frozen plasma is the standard treatment for bleeding manifestations. Recently, a novel plasma-derived FV concentrate has been developed. Aim To evaluate the "in vitro" ability of the novel FV concentrate to normalize clotting times and generate normal amount of thrombin in plasma collected from patients with severe FV deficiency. Methods Prothrombin time (PT), activated partial thromboplastin time (aPTT), FV activity and antigen levels and thrombin generation were measured pre- and postspiking of plasma samples of 10 patients with increasing doses of FV concentrate (from 0 to 100 IU/dL). Results Prothrombin time and activated partial thromboplastin time ratios as well as all thrombin generation parameters were fully corrected by the addition of FV concentrate at a final concentration of 25 IU/dL. However, the addition of FV at a concentration of 1-3 IU/dL was already sufficient to correct peak height and endogenous thrombin potential (but not lag time and time to peak) after activation with 5 pmol/L tissue factor. FV activity and antigen levels showed a linear response to supplementation with the novel FV concentrate. Conclusion The novel plasma-derived FV concentrate was effective to correct "in vitro" severe FV deficiency in patients. The optimal FV concentration to fully normalize both global clotting times and thrombin generation parameters using the novel plasma-derived FV concentrate was 25 IU/dL.

Coagulation factor V (FV) deficiency is a rare autosomal recessive bleeding disorder. We investigated a patient with severe FV deficiency (FV:C 3%) and moderate bleeding symptoms. Thrombin generation experiments showed residual FV expression in the patient's plasma, which was quantified as 0.7 ± 0.3% by a sensitive prothrombinase-based assay. F5 gene sequencing identified a novel missense mutation in exon 4 (c.578GC, p.Cys193Ser), predicting the abolition of a conserved disulphide bridge, and an apparently synonymous variant in exon 8 (c.1281CG). The observation that half of the patient's F5 mRNA lacked the last 18 nucleotides of exon 8 prompted us to re-evaluate the c.1281CG variant for its possible effects on splicing. Bioinformatics sequence analysis predicted that this transversion would activate a cryptic donor splice site and abolish an exonic splicing enhancer. Characterization in a F5 minigene model confirmed that the c.1281CG variant was responsible for the patient's splicing defect, which could be partially corrected by a mutation-specific morpholino antisense oligonucleotide. The aberrantly spliced F5 mRNA, whose stability was similar to that of the normal mRNA, encoded a putative FV mutant lacking amino acids 427-432. Expression in COS-1 cells indicated that the mutant protein is poorly secreted and not functional. In conclusion, the c.1281CG mutation, which was predicted to be translationally silent and hence neutral, causes FV deficiency by impairing pre-mRNA splicing. This finding underscores the importance of cDNA analysis for the correct assessment of exonic mutations.

Summary. Background and Objectives: The factor (F) V Leiden mutation causes activated protein C (APC) resistance by decreasing the susceptibility of FVa to APC-mediated inactivation and by impairing the APC-cofactor activity of FV in FVIIIa inactivation. However, APC resistance and the risk of venous thromboembolism (VTE) vary widely among FV Leiden heterozygotes. Common F5 genetic variation probably contributes to this variability. Patients/methods: APC resistance was determined in 250 FV Leiden heterozygotes and 133 normal relatives using the prothrombinase-based assay, which specifically measures the susceptibility of plasma FVa to APC. The effects of 12 F5 single-nucleotide polymorphisms (SNPs) on the normalized APC sensitivity ratio (nAPCsr) and on FV levels were determined by multiple regression analysis. Results: In FV Leiden heterozygotes, VTE risk increased with increasing nAPCsr, reaching an odds ratio (OR) of 9.9 (95% confidence interval [CI] 1.2–80.5) in the highest nAPCsr quartile. The minor alleles of several F5 SNPs, including 327 A/G (Q51Q), 409 G/C (D79H), 2663 A/G (K830R, T2 haplotype), 6533 T/C (M2120T) and 6755 A/G (D2194G, R2 haplotype), increased the nAPCsr in FV Leiden heterozygotes, but not in their normal relatives. Most of these effects could be attributed to a shift in the FVLeiden/normal FV ratio. Four FV Leiden heterozygotes with extremely high nAPCsr turned out to be pseudo-homozygotes, i.e. they carried a deleterious mutation on the non-Leiden allele. Conclusions: In FV Leiden heterozygotes, the prothrombinase-based nAPCsr is a marker of VTE risk and is modulated by common F5 SNPs that affect the FVLeiden/normal FV ratio in plasma.

Severe factor V (FV) deficiency (parahaemophilia) is a rare congenital hemorrhagic disorder characterized by very low or undetectable plasma FV levels and bleeding phenotype ranging from mild to severe. We evaluated whole blood (WB) rotation thromboelastometry (ROTEM) in parahaemophilia patients and the contribution of intraplatelets FV, if any, to clot formation. Standard ROTEM(®) assays were performed in WB from nine parahaemophilia patients and 50 healthy controls. In addition, platelets poor plasma from one parahaemophilia patient (PPP-Pt) or normal subjects (PPP-N) was reconstituted with washed platelets obtained either from one patient with parahaemophilia (Plts-Pt) or normal subjects (Plts-N) and ROTEM assays were performed in platelets rich plasma (PRP) samples. There was a prolongation of the WB clotting time (CT) in all assays in patients as compared with controls. However, maximum clot firmness (MCF) was similar in patients and controls. ROTEM in PPP-Pt showed both a prolongation of CT and a reduction of MCF as compared with PPP-N. The addition of either Plts-Pt or Plts-N to PPP-Pt resulted in similar increase in MCF and a decrease of CT which was more evident for PPP-Pt + Plts-N than PPP-Pt + Plts-Pt. In contrast, the addition of Plts-Pt or Plts-N to PPP-N had superimposable effects on both CT and MCF. In parahaemophilia patients, WB ROTEM(®) presents mainly with prolongation of CT and no relevant effect on MCF. Residual intraplatelets FV in parahaemophilia contributes significantly to thrombin generation as shown in artificially reconstituted PRP models.

Introduction The imbalance in clotting homeostasis, tending towards hypercoagulation, is recognized as the real barrier to the long-term survival of porcine xenografts in pig-to-primate xenotransplatation. The present study aimed to validate in primate blood the applicability of whole blood rotation thromboelastometry, performed by ROTEM®, which evaluates the characteristics of clot formation by dynamic monitoring. Materials and Methods ROTEM® (Pentapharm GmbH, Munich, Germany) was used to investigate native coagulation (NATEM®), the intrinsic (INTEM®) and extrinsic (EXTEM®) pathways, the function of fibrinogen (FIBTEM®), and the presence of fibrinolysis in 40 naive cynomolgus monkeys. Using classic validation approaches, the normal thromboelastographic profile was defined and the influence of haematocrit (Hct,%), platelet count (x10 9 /L), fibrinogen (mg/dl), and factor VIII (FVIII,%) was evaluated. Results In all four (NATEM®, INTEM®, EXTEM®, FIBTEM®) assays considered, Clotting Time (CT, sec) and Clot Formation Time (CFT, sec) were shorter in primates than humans. Moreover, α-angle (°), Maximum Clot Firmness (MCF, mm), and MaxVel (mm/min) were also higher in primates than humans. No substantial difference was observed for Hct and platelet count between the two species. On the contrary, FVIII was higher in primates than in humans whereas, interestingly enough, fibrinogen levels were lower in monkeys than in humans. Conclusion ROTEM® depicts a hypercoagulable profile in primates as compared to humans. Taken together these data suggest that, with regard to coagulation, xenotransplantation in cynos may represent a much more difficult situation than xenotransplantation in humans.

We report a case of juvenile thrombophilia associated with a substitution of leucine for arginine at position 338 (R338L) in the factor IX gene (factor IX-R338L). The level of the mutant factor IX protein in plasma was normal, but the clotting activity of factor IX from the proband was approximately eight times the normal level. In vitro, recombinant factor IX-R338L had a specific activity that was 5 to 10 times as high as that in the recombinant wild-type factor IX. The R338 substitution causes a gain-of-function mutation, resulting in factor IX that is hyperfunctional.

SummaryMany subjects carrying inherited thrombophilic defects will never experience venous thromboembolism (VTE) while other individuals developed recurrent VTE with no known additional risk factors. High levels of circulating microparticles (MP) have been associated with increased risk of VTE in patients with factor V Leiden and prothrombin G20210A mutation, suggesting a possible contribution of MP in the hypercoagulability of mild genetic thrombophilia. The role of MP as additional risk factor of VTE in carriers of natural clotting inhibitors defects (severe thrombophilia) has never been assessed. Plasma levels of annexin V-MP, endothelial-derived MP (EMP), platelet-derived MP (PMP), tissue factor-bearing MP (TF+) and the MP procoagulant activity (PPL) were measured in 132 carriers of natural anticoagulant deficiencies (25 antithrombin, 63 protein C and 64 protein S defect) and in 132 age and gender-matched healthy controls. Carriers of natural anticoagulant deficiencies, overall and separately considered, presented with higher median levels of annexin V-MP, EMP, PMP, TF+MP and PPL activity than healthy controls (p< 0.001, < 0.001, < 0.01, 0.025 and 0.03, respectively). Symptomatic carriers with a previous episode of VTE had significantly higher median levels of annexin-V MP than those without VTE (p=0.027). Carriers with high levels of annexin V-MP, EMP and PMP had an adjusted OR for VTE of 3.36 (95 % CI, 1.59 to 7.11), 9.26 (95 % CI, 3.55 to 24.1) and 2.72 (95 %CI, 1.16 to 6.38), respectively. Elevated levels of circulating MP can play a role in carriers of mild and severe inherited thrombophilia. The clinical implications of this association remain to be defined.

Some members of the glutathione peroxidase (GPx) family have been reported to accept thioredoxin as reducing substrate. However, the selenocysteine-containing ones oxidise thioredoxin (Trx), if at all, at extremely slow rates. In contrast, the Cys homolog of Drosophila melanogaster exhibits a clear preference for Trx, the net forward rate constant, k'(+2), for reduction by Trx being 1.5x10(6) M(-1) s(-1), but only 5.4 M(-1) s(-1) for glutathione. Like other CysGPxs with thioredoxin peroxidase activity, Drosophila melanogaster (Dm)GPx oxidized by H(2)O(2) contained an intra-molecular disulfide bridge between the active-site cysteine (C45; C(P)) and C91. Site-directed mutagenesis of C91 in DmGPx abrogated Trx peroxidase activity, but increased the rate constant for glutathione by two orders of magnitude. In contrast, a replacement of C74 by Ser or Ala only marginally affected activity and specificity of DmGPx. Furthermore, LC-MS/MS analysis of oxidized DmGPx exposed to a reduced Trx C35S mutant yielded a dead-end intermediate containing a disulfide between Trx C32 and DmGPx C91. Thus, the catalytic mechanism of DmGPx, unlike that of selenocysteine (Sec)GPxs, involves formation of an internal disulfide that is pivotal to the interaction with Trx. Hereby C91, like the analogous second cysteine in 2-cysteine peroxiredoxins, adopts the role of a "resolving" cysteine (C(R)). Molecular modeling and homology considerations based on 450 GPxs suggest peculiar features to determine Trx specificity: (i) a non-aligned second Cys within the fourth helix that acts as C(R); (ii) deletions of the subunit interfaces typical of tetrameric GPxs leading to flexibility of the C(R)-containing loop. Based of these characteristics, most of the non-mammalian CysGPxs, in functional terms, are thioredoxin peroxidases.

Background Activation of the clotting cascade is central in acute xenograft rejection (AHXR) that occurs when pig organs are transplanted into primates. The coagulopathy reported in this model is a very complex process that involves simultaneously coagulation factors, platelets and phospholipid-bearing cells (i.e., leukocytes, red blood cells, and endothelial cells). Choosing whole blood for coagulation analysis theoretically appears more favorable compared with plasma. Whole blood rotation thromboelastometry (ROTEM®) is a point-of-care global coagulation analyzer able to evaluate the characteristics of clot formation and lysis by dynamic monitoring. The aim of this study was to record thromboelastographic profiles, performed by ROTEM®, in a series of immunosuppressed nephrectomized primates that received a life-supporting kidney. Methods Of the eight primates, n = 4 received a pig kidney transgenic for human decay-accelerating factor (hDAF/Gal+); n = 2, an α 1,3-galactosyltransferase gene-knockout (GT-KO) pig kidney transgenic for human CD39, CD55, CD59 and fucosyltransferase (HTF); and n = 2, a GT-KO pig kidney transgenic for hDAF. Blood samples were collected before and at least once per week after transplantation till euthanasia. Intrinsic (INTEM) and extrinsic (EXTEM) coagulation pathways and the function of fibrinogen (FIBTEM) were evaluated. Thromboelastographic parameters considered were clotting time (CT, seconds) and clot formation time (CFT, seconds) in INTEM and EXTEM and maximum clot firmness (MCF, mm) in FIBTEM. The correlations between CT in INTEM and activated partial thromboplastin time (aPTT), CT in EXTEM and PT, CFT in INTEM and EXTEM, and platelet counts and MCF in FIBTEM and fibrinogen plasma levels were also considered. Results In all animals, thromboelastographic profiles showed progressive prolongation of CT (activation of coagulative cascade) in INTEM. A close correspondence was observed between (i) the prolongation of the CFT values (propagation of clot formation), both in INTEM and EXTEM, and the decrease in platelet counts; (ii) the reduction in MCF values (clot firmness) ​​in FIBTEM and the decrease in fibrinogen plasma levels. No concordance between CT in INTEM and aPTT and between CT in EXTEM and PT was observed. Conclusions Our study demonstrated that ROTEM® analyzer could be a useful and complementary tool to study the consumptive coagulopathy, either “compensated” or “non-compensated,” that takes place when transgenic pig kidneys are transplanted into primates. Larger and prospective studies are needed to confirm our results and to evaluate the role of ROTEM® to guide the management of consumptive coagulopathy in order to prolong the survival of the transplanted organ.

Microvascular thrombosis, following the activation of clotting cascade, is a hallmark of porcine solid organ xenograft rejection. The analysis of differences between human, monkey, and pig coagulation systems is crucial when monkey is used as animal model and pig as organ donor in xenotransplantation. Thrombosis, according to many authors, may be due to the molecular incompatibilities between natural anticoagulants present on pig endothelium and primate activated coagulation factors. The generation of activated protein C (PC) is critical for the physiological anticoagulation. One of the major incompatibilities may be related to the inability of pig thrombomodulin (TM) and endothelial protein C receptor to activate the recipient (primate) circulating PC in the presence of thrombin. Tissue factor pathway inhibitor (TFPI), is the primary inhibitor of tissue factor (TF)-induced coagulation. TFPI directly inhibits the activated factor X (FXa) and blocks the procoagulant activity of the TF/factor VIIa (FVIIa) complex by forming a quaternary TF/FVIIa/FXa/TFPI complex. Microvascular thrombosis, observed in the organ transplant, may also be due to the failure of pig TFPI to bind human FXa efficiently and inhibit human FVIIa/TF activity. The methods described in this chapter can be useful for the identification and characterization of primate and pig coagulation factors (isolated from a small volume of blood) by using SDS-PAGE and immunoblotting. Differences in molecular weight can help in the identification of the origin (pig or primate) of coagulation proteins in plasma from the recipient of xenografts. On the other hand, in vitro models of PC pathway and TFPI on human umbilical vein endothelial cells (HUVEC) and porcine aortic endothelial cells (PAEC) are described which can be used for studying incompatibilities between primate and pig.

BACKGROUND The role potential of recombinant human activated protein C (rhaPC), a recently developed molecule with anticoagulant and antiinflammatory properties, in prolonging survival in immunosuppressed primate recipients of porcine renal xenografts has been evaluated. METHODS rhaPC was administered daily for 5 days (24 μg/kg/hr; group A; n = 3) or throughout the postoperative period (8-24 μg/kg/hr; group B; n = 2; or 24-48 μg/kg/hr; group C; n = 4). Animals in group D (n = 2) received rhaPC daily (24 μg/kg/hr) combined with recombinant human antithrombin (84 U/kg every 8 hr). Two animals served as control (group E). RESULTS The results indicate that rhaPC is protective against fibrin deposition early after transplantation but does not prevent fibrin deposition and the occurrence of acute humoral xenograft rejection (AHXR) later on. Animals in the study survived between 8 and 55 days. At the dose used, rhaPC is able to prevent fibrin deposition in the graft in the first 2 weeks after xenotransplantation, except when it is administered in conjunction with antithrombin. However, rhaPC did not prevent the eventual occurrence of AHXR in primate recipients of porcine xenografts. CONCLUSIONS In this pig to primate model, rhaPC confers a short advantage in the prevention of early perioperative xenograft damage but does not represent an effective strategy for preventing AHXR.

Cancer is a prothrombotic state, with an increased prevalence of venous thromboembolism (VTE). Microparticles (MPs) are sub-micron-sized vesicles derived from activated or apoptotic cells that may play a role in VTE, although evidence of this association is still limited.To evaluate the hypothesis that elevated numbers of endothelial (EMPs), platelets (PMPs), and Tissue Factor-bearing MPs (TF(+)MPs) in plasma may contribute to cancer-associated thrombosis.EMPs, PMPs and TF(+)MPs plasma levels were measured in 90 consecutive patients (cases) referred to our Department (30 with a first episode of unprovoked VTE; 30 with active cancer; 30 with a diagnosis of acute VTE associated with active cancer), and in a group of 90 healthy subjects (controls). MPs analyses were performed by flow-cytometry (Cytomics FC500).Cases showed statistically significant higher (mean ± SD) circulating EMPs and PMPs plasma levels (920 ± 341 and 1221 ± 413 MP/μL, respectively) than controls (299 ± 102 and 495 ± 241 MP/μL; p0.005). Moreover cancer patients (with and without VTE) showed higher (mean ± SD) TF(+)MPs (927 ± 415 MPs/μL) than controls (204 ± 112 MPs/μL; p0.001). The subgroup of cancer patients plus VTE showed statistically significant higher TF(+)MPs plasma levels (1019 ± 656 MPs/μL) than cancer patients without VTE (755 ± 391 MPs/μL, p = 0.002). Multivariate analysis failed to show a significant association between elevated TF(+)MPs and VTE in cancer patients.Our results suggest that MPs might be an important intermediate in the cascade of cellular injury and vascular dysfunctions underlying the process of thrombosis, particularly in cancer. Further clinical investigations are needed to confirm the precise role of MPs in predicting hypercoagulable state in patients with cancer.

The present study aimed at elucidating the mechanism(s) of serotonin (5-HT) efflux induced by thapsigargin from human platelets in the absence of extra-cellular Ca2+.Efflux of pre-loaded radiolabeled serotonin was generally determined by filtration techniques. Cytosolic concentrations of Ca2+, Na+ and H+ were measured with appropriate fluorescent probes.5-HT efflux from control or reserpine-treated platelets--where reserpine prevents 5-HT transport into the dense granules--was proportional to thapsigargin evoked cytosolic [Ca2+]c increase. Accordingly factors as prostacyclin, aspirin and calyculin which reduced [Ca2+]c-increase also inhibited the 5-HT efflux. Thapsigargin, which also caused a remarkable increase in cytosolic [Na+]c, promoted less 5-HT release, in parallel to lower [Na+]c and [Ca2+]c increase, when added to platelet suspensions containing low [Na+]. The Na+/H+ exchanger monensin increased the [Na+]c and induced 5-HT efflux without affecting the Ca2+ level. The 5-HT efflux induced by both [Ca2+] or [Na+]c increase did not depend on pH or membrane potential changes, whereas it decreased in the absence of extra-cellular K+, and increased in the absence of Cl- or Na+.Increases in [Ca2+]c and [Na+]c independently induce serotonin efflux through the outward directed plasma membrane serotonin transporter SERT. This event might be physiologically important at the level of capillaries or narrowed arteries where platelets are subjected to high shear stress which causes [Ca2+]c increase followed by 5-HT release which might exert vasodilatation.